Gaskets used in combination with pipe joints, and manhole shields have been known to exist in the prior art for some time. Those patents which reflect the prior art as the inventor is aware comprise the following:
______________________________________ 393,684 Berryhill 3,787,061 Yoakum 2,226,304 Dillon 3,787,078 Williams 2,822,192 Beatty 3,850,457 Bigotte et al 3,142,234 Maloon 4,009,545 Rossborough 3,360,273 Hundt et al 4,073,048 Ditcher 3,759,280 Swanson 4,102,088 Keller et al ______________________________________
The patent to Hundt et al can be distinguished from the instant application by noting that this type of a gasket is typically used for a bell and spigot type pipe joint. The fluid in the instant application does not solidify or take a permanent set, and the unique structure associated with the instant application provides the ability to attenuate vibration, pump start or water hammer vibrations, as well as the natural shifting of one element relative to the other.
Similarly, Berryhill teaches the use of a joint seal for a bell and spigot arrangement wherein that specific structure is neither suitable for nor compatible with the use defined in the instant application.
The remaining references diverge even further from that which is taught in the instant application.